Bats roosting in Walls Unit

Mexican free-tailed bats roosting inside the cotton warehouse across from the Walls Unit.

Gary McCracken, professor emeritus from the University of Tennessee, Knoxville, was the guest speaker at a seminar on bats hosted by the Huntsville Bat Society and the Sam Houston State Museum of Natural Science on Friday. McCracken offered extensive research on the Mexican free-tailed bat, the species inhabiting the cotton warehouse across from the Walls Unit. Nate Fuller of Texas Parks and Wildlife was also there to offer information and solutions to the quandary, which has been a subject of concern in Huntsville since 1997.

The good news is that Texas Department of Corrections (TDC) officials are open to investing in a solution and have given Fuller and the Bat Society a year to present viable options. Fuller is pursuing a matching grant with a wind energy company to secure funding for the project. Robin Logan, co-founder of the bat society, has established a non-profit organization called Building for Bats to spearhead the efforts. 

“There are a lot of legalities and planning involved,” said Logan. “TDC allowed us a wonderful opportunity for documentation and is 100% open to solutions.” The board of the new non-profit includes directors from TDC, a former warden, a conservationist, biology professors from SHSU and a city representative from the tourism department.

Logan, McCracken and Fuller toured the cotton warehouse on Friday morning with Jason Pierce of TDC. Based on their prior experiences with bat colonies, it could take up to five years for the colony to relocate to an artificial cave in the best of circumstances. The size of this colony is estimated at nearly a million bats. The complexity of the habitat is very important, which is why the bats did not relocate to the new bat houses that were built by TDC in 2017. 

The warehouse is diverse, offering an amenable shape and temperature that is similar to a natural cave. Replicating the habitat is possible, but complicated. The known factor is that if the roof is removed or the building is demolished, the bats will relocate to the nearest locations that suit them. 

McCracken’s area of expertise is Ecology and Evolutionary biology. He has studied bats for more than 40 years, researching their migratory patterns and roosting habits across many locations, specifically in Texas. He says this colony is full service. They roost, mate, give birth and raise their young in this location. The species is largely migratory, but extreme weather conditions tied to climate change have caused an increasing number to remain close to their roost over the winter in recent years.

Fuller is a bat biologist who investigates declines in bat colonies to enforce their protection, assisting Texas Parks and Wildlife to identify and deliver fines to individuals or entities who disturb or eradicate their habitats. Fuller served as part of a research team at the Bamberger Ranch Preserve near Johnson City, where McCracken was a consultant. They assisted the owner in gathering sufficient data to build a chiroptorium, which is a man-made cave to attract and house bat colonies. For those who discount the importance of bats, it has to do with ecology.

“I have been repeatedly impressed by the value of urban bat colonies for pest control,” said McCracken. “An average bat will eat up to 50% of its body weight in insects every night. A mother bat who is lactating will consume as much as 70%. They also fly as far as 100 miles from their roost to feed.” 

According to McCracken's calculations, this colony consumes 10 metric tons of insects nightly. Contrary to popular belief, they don’t consume many mosquitoes. But they do favor worms and other pests that destroy crops.

In research shared by McCracken and Fuller, bats consume 12 different orders of insects, including 21 species of migrating pests. Ten years ago, the USDA estimated the value of this natural pest control service at $93 per hectare in Central Texas, which represented 12% of the market value of cotton. The overall value to U.S. agriculture at that time was factored between $3.7 and $5.3 billion. 

The value of bats as a tourist attraction is another matter to be considered. According to statistics presented by McCracken, Carlsbad Caverns reported $3.5 million in economic benefits from tourism related to bats ten years ago. In 2021, that figure had risen to $27.4 million. The Congress Street Bridge in Austin is estimated to have generated roughly $10 million in bat-related tourism in 2020.

For those closely involved with the project, the best case scenario would be for the bat colony to become the focus of a research center. Bats are sensitive to environmental contaminants and are reliable indicators of a healthy ecosystem. Although they are not an endangered species, they are protected by state and federal regulations. 

According to Fuller, the law states that a landowner in Texas may not kill, hunt, or harass a bat unless it is in or on a building inhabited by humans. Buying, selling or possessing one is prohibited. Using chemicals to eradicate them is also illegal. The fine for killing a single bat is $800. Anyone who finds a dead bat is asked to send a report with a picture and approximate location to

Huntsville Bat Society was founded by Robin Logan and Daiquiri Beebe. Follow their page on Facebook at To support the non-profit organization Building for Bats, visit For more information about Mexican free-tailed bats, visit Bat Conservation International at

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